Low activation energy dissolution modification agents for photoresist applications

ABSTRACT

A dissolution modification agent suitable for use in a photoresist composition including a polymer, a photoacid generator and casting solvent. The dissolution modification agent is insoluble in aqueous alkaline developer and inhibits dissolution of the polymer in the developer until acid is generated by the photoacid generator being exposed to actinic radiation, whereupon the dissolution modifying agent, at a suitable temperature, becomes soluble in the developer and allows the polymer to dissolve in the developer. The DMAs are glucosides, cholates, citrates and adamantanedicarboxylates protected with acid-labile ethoxyethyl, tetrahydrofuranyl, and angelicalactonyl groups.

RELATED APPLICATIONS

This Application is a division of application Ser. No. 11/239,507 filedon Sep. 29, 2005 now U.S. Pat. No. 7,358,029.

FIELD OF THE INVENTION

This invention relates generally to the field of photolithography. Morespecifically, the invention relates to chemically amplified photoresistsystem compositions containing dissolution modification agents, methodsof using chemically amplified photoresist system compositions containingdissolution modification agents and dissolution modification agents forchemically amplified resist systems.

BACKGROUND OF THE INVENTION

The patterning of radiation sensitive polymeric films with actinicradiation such as ultraviolet light at wavelengths of 436, 365, 257,248, 193 or 157 nanometers (nm) is the principle means of defining highresolution circuitry found in semiconductor devices. The radiationsensitive films, often referred to as photoresists, generally consist ofmulti-component formulations that are coated onto a desired substrate.The radiation is exposed patternwise and induces a chemicaltransformation that renders the solubility of the exposed regions of thefilms different from that of the unexposed areas when the films aretreated with an appropriate developer.

Chemically amplified photoresists are based on a catalytic mechanismthat allows a relatively large number of chemical events such as, forexample, de-protection reactions in the case of positive photoresists orcross-linking reactions in the case of negative tone photoresists, to bebrought about by the application of a relatively low dose of radiationthat induces formation of a catalyst, often a strong acid. However,chemically amplified photoresists, particularly in the sub-50 nm regime,experience diminished image resolution or contrast, often referred to as“image blur.”

Therefore, there is an ongoing need for new photoresist compositionshaving improved image resolution capability as well as improved methodsof patterning substrates.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a dissolution agentrepresented by one of the following structures:

wherein each P¹, P², P³, P⁴, P⁵, P⁶, P⁷, P⁸, and P¹⁵ is independentlyselected from the group consisting of a structure V, a structure VI anda structure VII:

wherein each R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is independently selectedfrom the group consisting of a hydrogen atom, a hydrocarbyl group having4 to 12 carbon atoms, a substituted hydrocarbyl group having 4 to 12carbon atoms, a heterohydrocarbyl group having 4 to 12 carbon atoms, anda substituted heterohydrocarbyl group having 4 to 12 carbon atoms; and

wherein any two R¹, R², R³ or any two R⁴, R⁵, R⁶ may be linked to form athree to eight-membered cyclic group.

BRIEF DESCRIPTION OF DRAWINGS

The features of the invention are set forth in the appended claims. Theinvention itself, however, will be best understood by reference to thefollowing detailed description of an illustrative embodiment when readin conjunction with the accompanying drawings, wherein:

FIGS. 1A through 1G are cross-sectional views of an exemplaryphotoresist patterning method according to the various embodiments ofthe present invention;

FIG. 2A is plot of photoresist thickness versus post exposure baketemperature for a control photoresist formulation;

FIG. 2B is plot of photoresist thickness versus post exposure baketemperature for an experimental photoresist formulation according to anembodiment of the present invention; and

FIG. 3 is plot of photoresist thickness versus actinic radiation dose asa function of post exposure bake temperature for an experimentalphotoresist formulation according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Chemically amplified (CA) positive photoresists described by the variousembodiments of the present invention are intended to be developed in anaqueous developer and include a polymer that is soluble in an aqueousalkaline solution, a dissolution modification agent (DMA), and aphotoacid generator (PAG), all usually dissolved in a casting solvent.The PAG generates acid upon exposure to actinic radiation.

Image blur in such a photoresist system is generally thought to resultfrom two contributing factors: gradient-driven diffusion of acid fromexposed into non-exposed regions and reaction propagation. Aciddiffusion is thought to depend upon such factors as the type of PAG andacid moiety mobility in the photoresist polymer. Acid mobility in aphotoresist layer is dependent on a variety of factors, including thechemical functionality of the polymer and the temperature of thephotoresist layer. Reaction propagation is thought to depend upon suchfactors as the activation energy (enthalpy) and the volatility ofreaction products (entropy). Both acid diffusion and acid mobilityincrease with increasing temperature with resultant increasing imageblur.

DMAs according to various embodiments of the present invention arehydrophobic and insoluble in aqueous alkaline developer, thus inhibitingpolymer dissolution in the unexposed regions of photoresist layers. Insome examples, the polymer itself may be soluble in aqueous alkalinedeveloper, but is inhibited from dissolving in the developer by thestrong hydrophobic nature of the DMA. At the same time, DMAs accordingto various embodiments of the present invention, when activated, becomehydrophilic and soluble in aqueous alkaline developer and thus enhancepolymer dissolution in the exposed regions of photoresist layers. Whenactivated, the DMA become soluble and hydrophilic and no longer inhibitssolution of the polymers in the exposed regions of the photoresistlayer. DMAs are activated by the acid released by the PAG attemperatures dependent upon the activation energy of protectedacid-labile moieties of the DMAs.

Since it is advantageous to minimize the temperature to which exposedphotoresist layers are subjected (to minimize image blur), the variousembodiments of the present invention utilize DMAs that are relativelysmall molecules containing polar and/or base-soluble moieties which areprotected by low activation (e.g. low temperature) acid-labilefunctionalities.

FIGS. 1A through 1G are cross-sectional views of an exemplaryphotoresist patterning method according to the various embodiments ofthe present invention.

In FIG. 1A, formed on a top surface 100 of a substrate 105 is anoptional insulating layer 110. In one example, substrate 100 is selectedfrom the group consisting of a metal substrate, a ceramic substrate, anorganic substrate, a bulk silicon substrate, a silicon-on-insulatorsubstrate and other semiconductor substrates. In one example, layer 110comprises silicon dioxide, silicon nitride, silicon oxynitride andcombinations thereof. Layer 110 may include other insulating materialsas is known in the art of integrated circuit manufacture. Alternatively,layer 110 may be replaced by a conductive layer or a semi-conductivelayer as is known in the art of integrated circuit manufacture.

Formed on a top surface 115 of layer 110 is an optional anti-reflectivecoating (ARC). In one example, ARC 115 comprises a diazonaphthoquinone(DNQ)/novolak resist material. ARC 115 may be formed on top surface 105of substrate 100 if there is no layer 110.

Formed on a top surface 125 of ARC 120 is a photoresist layer 130.Photoresist layer 130 may be formed by spin or spray coating, or doctorblading a layer of a photoresist composition on ARC 120, or on layer 110if there is no ARC 120 or on substrate 105 if there is no ARC 120 orlayer 110. The composition of photoresist layer 130, includes a one ormore polymers (at least one not soluble in aqueous alkaline developer),a PAG, a DMA and an optional casting solvent.

In one example, the DMA comprises a material represented by at least oneof one of the following (I, II, III, IV) structures:

wherein each R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is independently selectedfrom the group consisting of a hydrogen atom, a hydrocarbyl group having4 to 12 carbon atoms, a substituted hydrocarbyl group having 4 to 12carbon atoms, a heterohydrocarbyl group having 4 to 12 carbon atoms, anda substituted heterohydrocarbyl group having 4 to 12 carbon atoms; and

wherein any two R¹, R², R³ or any two R⁴, R⁵, R⁶ may be linked to form athree to eight-membered cyclic group.

wherein W and X are independently selected from the group consisting ofan alkylene group having 1 to 12 carbon atoms, and a fluorinatedalkylene group having 1 to 12 carbon atoms;

wherein each P¹, P², P³, P⁴, P⁵, P⁶, P⁷, P⁸, P⁹, P¹⁰, P¹¹, P¹², P¹³,P¹⁴, and P¹⁵ is independently selected from the group consisting of astructure V, a structure VI and a structure VII:

wherein each R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is independently selectedfrom the group consisting of a hydrogen atom, a hydrocarbyl group having4 to 12 carbon atoms, a substituted hydrocarbyl group having 4 to 12carbon atoms, a heterohydrocarbyl group having 4 to 12 carbon atoms, anda substituted heterohydrocarbyl group having 4 to 12 carbon atoms; and

wherein any two R¹, R², R³ or any two R⁴, R⁵, R⁶ may be linked to form athree to eight-membered cyclic group.

Structure I is a glucoside, structure II is a citrate, structure III isa cholate and structure IV is an adamantanedicarboxylate. The protectinggroup of structure V is an ethoxyethyl group, the protecting group ofstructure VI is a tetrahydrofuranyl group, and the protecting group ofstructure VII is an angelicalactone.

In a first example, the polymer comprises repeating units of one or moremonomers represented by the following structures:M¹-R⁸  (VIII_(i))M²-R⁹  (VIII_(ii))M³-R¹⁰  (VIII_(iii))

where M¹, M² and M³ are independently selected from the group consistingof an alkylene group having 2 to 12 carbon atoms, a substituted alkylenegroup having 2 to 12 carbon atoms, a heteroalkylene group having 2 to 12carbon atoms, a substituted heteroalkylene group having 2 to 12 carbonatoms, an alicyclic group having 3 to 15 carbon atoms, and afluoroalicyclic group having 3 to 15 carbon atoms;

where R⁸ has a structure —R¹¹—CR¹²R¹³—OH, in which:

R¹¹ is selected from the group consisting of an alkylene group having 2to 12 carbon atoms, a substituted alkylene group having 2 to 12 carbonatoms, a heteroalkylene group having 2 to 12 carbon atoms, a substitutedheteroalkylene group having 2 to 12 carbon atoms, an alicyclic grouphaving 3 to 15 carbon atoms, and a fluoroalicyclic group having 3 to 15carbon atoms;

R¹² is selected from the group consisting of a hydrogen atom, an alkylgroup having 1 to 24 carbon atoms, a substituted alkyl group having 1 to22 carbon atoms, and a fluorinated alkyl group having 1 to 24 carbonatoms;

R¹³ is selected from the group consisting of a hydrogen atom, an alkylgroup having 1 to 24 carbon atoms, and a fluorinated alkyl group having1 to 24 carbon atoms; and

wherein R¹² and R¹³ may be linked to form a 3 to 8 carbon atom cyclicring;

wherein R⁹ has a structure —R¹⁴—NH—SO₂R¹⁵, in which:

R¹⁴ is selected from the group consisting of an alkylene group having 2to 12 carbon atoms, a substituted alkylene group having 2 to 12 carbonatoms, a heteroalkylene group having 2 to 12 carbon atoms, a substitutedheteroalkylene group having 2 to 12 carbon atoms, an alicyclic grouphaving 3 to 15 carbon atoms, and a fluoroalicyclic group having 2 to 12carbon atoms; and

R¹⁵ is selected from the group consisting of a hydrogen atom, an alkylgroup having 1 to 24 carbon atoms, a fluorinated alkyl group having 1 to24 carbon atoms, a substituted alkyl group having 1 to 24 carbon atoms,and a fluorinated alkyl group having 1 to 24 carbon atoms; and

wherein R¹⁰ has a structure —R¹⁶—COOH, in which:

R¹⁶ is selected from the group consisting of an alkylene group having 2to 12 carbon atoms, a substituted alkylene group having 2 to 12 carbonatoms, a heteroalkylene group having 2 to 12 carbon atoms, a substitutedheteroalkylene group having 2 to 12 carbon atoms, an alicyclic grouphaving 3 to 15 carbon atoms, and a fluoroalicyclic group having 3 to 15carbon atoms.

In a second example, the polymer comprises repeating units of one ormore monomers represented by the following structures:

wherein each R¹⁸, R¹⁹, R²⁰, R²¹, R²², R²³, R²⁴, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹,R³⁰, R³¹, R³², R³³, R³⁴, R³⁵, R³⁶, R³⁷, R³⁸, R³⁹, R⁴⁰, R⁴¹ R⁴², R⁴³,R⁴⁴, R⁴⁵, R⁴⁶ and R⁴⁷ (R¹⁸-R⁴⁷) is independently selected from the groupconsisting of a hydrogen atom and a hydrocarbyl substituent with aprimary, secondary or tertiary carbon attachment point, said hydrocarbylsubstituent selected from the group consisting of a linear alkyl or analkoxy group having 1-6 carbon atoms, a branched alkyl group having 2-12carbon atoms, an alkoxy group having 2-12 carbon atoms, a cycloalkylgroup having 3-17 carbon atoms, a bicycloalkyl group having 3-17 carbonatoms, a cycloalkoxy having 3-17 carbon atoms, a bicycloalkoxy grouphaving 3-17 carbon atoms, a fluorinated linear alkyl group having 2-12carbon atoms, a fluorinated branched alkyl group having 2-12 carbonatoms, a fluorinated cycloalkyl group having 3-17 carbon atoms, analkenyl group having 2-12 carbon atoms, a cycloalkenyl group having 2-12carbon atoms, a dihydropyranyl group, a dihydrofuranyl group, analkalkenyl group having 2-12 carbon atoms, an alkenylalkyl group having2-12 carbon atoms, an alkynyl group having 2-12 carbon atoms, analkalkynyl group having 2-12 carbon atoms, an alkynylalkyl group having2-12 carbon atoms, a trifluoromethyl group, a trifluoroethyl group, atrifluoropropyl group, and a cyanopropyl group; and

wherein any two of R¹⁸-R²⁰, R²¹-R³⁰, R³¹-R³⁹ and R⁴⁰-R⁴⁷ in the samemolecule may be linked to form a 3 to 8 carbon atom cyclic ring.

In a third example, the polymer comprises repeating units of one or moremonomers represented by the following structures:

In a fourth example, the polymer comprises repeating units of one ormore monomers represented by the following structures:

In a fifth example, the polymer comprises repeating units of one or moremonomers represented by the following structures:

In a sixth example, the polymer comprises repeating units of one or moremonomers represented by the following structures:

wherein M is a polymerizable backbone moiety;

wherein each Y_(m) at each occurrence is independently selected from thegroup consisting of —C(O)O—, —C(O)—, —OC(O)—, —O—C(O)— and —C(O)—O—;

wherein each Z_(n) at each occurrence is independently selected from thegroup consisting of an alkylene group having 1 to 12 carbon atoms, afluorinated alkylene group having 1 to 12 carbon atoms, a heteroalkylenegroup having 1 to 12 carbon atoms, an alicyclic group having 3 to 15carbon atoms, and a fluoroalicyclic group having 3 to 15 carbon atoms;

wherein (a) m and n are both 1, (b) m is 1 and n is 0 or (c) m is 0 andn is 1; and

wherein each occurrence of R⁴⁸ is independently selected from the groupconsisting of a hydrogen atom, a hydroxyl group, a hydroxy substitutedalkylene having 1 to 12 carbon atoms, a hydroxy substitutedfluoroalkylene having 1 to 12 carbon atoms, abis-trifluoromethylmethanol group, and an alkylsulfonamide group having1 to 12 carbon atoms.

In a first example the PAG comprises a sulfonium salt.

In a second example, the PAG is selected from is selected from the groupconsisting of sulfonium salts, triphenylsulfoniumperfluoromethanesulfonate (triphenylsulfonium triflate),triphenylsulfonium perfluorobutanesulfonate, triphenylsulfoniumperfluoropentanesulfonate, triphenylsulfonium perfluorooctanesulfonate,triphenylsulfonium hexafluoroantimonate, triphenylsulfoniumhexafluoroarsenate, triphenylsulfonium hexafluorophosphate,triphenylsulfonium bromide, triphenylsulfonium chloride,triphenylsulfonium iodide, 2,4,6-trimethylphenyldiphenylsulfoniumperfluorobutanesulfonate, 2,4,6-trimethylphenyldiphenylsulfoniumbenzenesulfonate, tris(t-butylphenyl)sulfonium salts,diphenylethylsulfonium chloride, phenacyldimethylsulfonium chloride,halonium salts, diphenyliodonium perfluoromethanesulfonate(diphenyl)odonium triflate), diphenyliodonium perfluorobutanesulfonate,diphenyliodonium perfluoropentanesulfonate, diphenyliodonium salts,diphenyliodonium hexafluoroantimonate, diphenyliodoniumhexafluoroarsenate, bis-(t-butylphenyl)iodonium triflate,bis-(t-butylphenyl)-iodonium camphorsulfonate, a,α′-bis-sulfonyl-diazomethanes, bis(p-toluenesulfonyl)diazomethane,methylsulfonyl p-toluenesulfonyldiazomethane,1-cyclohexylsulfonyl-1-(1,1 dimethylethylsulfonyl) diazomethane,bis(cyclohexylsulfonyl)diazomethane, trifluoromethanesulfonate esters ofimides and hydroxyimides, (trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide (MDT), nitrobenzyl sulfonate esters,2-nitrobenzyl p-toluenesulfonate, 2,6-dinitrobenzyl p-toluenesulfonate,2,4-dinitrobenzyl p-trifluoromethylbenzenesulfonate;sulfonyloxynaphthalimides, N-camphorsulfonyloxynaphthalimide andN-pentafluorophenylsulfonyloxynaphthalimide; pyrogallol derivatives(e.g., trimesylate of pyrogallol), naphthoquinone-4-diazides, alkyldisulfones, s-triazine derivatives; sulfonic acid generators,N-hydroxynaphthalimide dodecane sulfonate (DDSN) and benzoin tosylate.

In one example the casting solvent is selected from the group consistingof cyclohexanone, ethyl lactate, propylene glycol methyl ether acetate,gamma-butyrolactone and combinations thereof.

In one example, the photoresist composition comprises about 8% by weightto about 15% by weight of polymer, about 1% by weight to about 3% byweight of PAG and about 10% by weight to about 15% by weight of DMA.

Preferably, before photoresist layer 130 is exposed to actinicradiation, the photoresist layer is heated to drive out casting solvent(pre-exposure baked or pre-baked) to a temperature of about 90° C. toabout 110° C. for about 1 minute. In one example, photoresist layer 130has a thickness of about 0.02 micron to about 5.0 microns, preferablyabout 0.05 micron to about 2.5 microns and most preferably about 0.10micron to about 1.0 microns.

In FIG. 1B, photoresist layer 130 is exposed to actinic radiation 135through an exemplary mask 140. Mask 140 includes a transparent substrate145 and opaque islands 150. Other types of masks such as phase contrastmasks may be used as well. Portions 135A of actinic radiation 135 passthrough transparent region 145 and strike photoresist layer 130 whileother portions of the actinic radiation are blocked by opaque islands150. In regions of photoresist layer 130 struck by portions 135A ofactinic radiation 135, the PAG in those regions generates an acid.Actinic radiation 135 may be ultraviolet, electron beam or x-ray.Ultraviolet radiation is preferred, particularly deep ultravioletradiation having a wavelength of less than about 250 nm and preferablyabout 193 nm or less.

In FIG. 1C, upon heating photoresist layer 130 (see FIG. 1B) to atemperature of between about 26° C. and about 100° C., preferably below80° C., more preferably below 50° C. and most preferably to just aboveroom temperature (about 26° C.), the acid generated by the PAG causescleavage of the acid-labile groups of the DMAs. This causes formation oflatent images 155 in photoresist layer 130. However, the acid-labilegroups of the DMAs in non-exposed regions of photoresist layer 130 arenot activated since no acid was generated by the PAG.

In FIG. 1D, photoresist layer 130 (see FIG. 1C) is developed in anaqueous alkaline solution of a strong base such as tetramethylammoniumhydroxide or choline to form photoresist islands 160. Any ARC 120 (seeFIG. 1C) not protected by photoresist islands 160 is also removedforming ARC islands 165 exposing top surface 115 of layer 110.

In FIG. 1E, layer 110 is etched, in one example, using a reactive ionetch (RIE) process to form islands 170 of layer 110 (see FIG. 1D) andexposing top surface 100 of substrate 105 where the substrate is notcovered by the islands.

In FIG. 1F, photoresist islands 160 and ARC islands 165 are removed.

The operation illustrated in FIG. 1G is optional. In FIG. 1G, trenches175 are formed in substrate 105, in one example, using a RIE process,islands 170 acting as a “hard” etch mask.

Alternatively, if there is no layer 110 (see FIG. 1A), trenches 175 areformed in substrate 105, in one example, using a RIE process,photoresist islands 160 (see FIG. 1D) acting as a “soft” etch mask.

General DMA Synthesis

The protected DMA glucosides (I), citrates (II), cholates (III) andadamantanedicarboxylates (IV) where the protecting group is representedby an ethoxyethyl group (V) were prepared by treatment of the glucoside,cholate, citrate or adamantanedicarboxylate with the acetal-formingreagent ethyl vinyl ether in the presence of pyridiniump-toluenesulfonate in ether or tetrahydrofuran (THF) solvent.

The protected DMA glucosides (I), citrates (II), cholates (III) andadamantanedicarboxylates (IV) where the protecting group is representedby a tetrahydrofuranyl group (VI) were prepared by treatment of theglucoside, cholate, citrate or adamantanedicarboxylate with theacetal-forming reagent dihydrofuran in the presence of pyridiniump-toluenesulfonate in ether or THF solvent.

The products were purified by silica gel column chromatography andcharacterized by H-NMR and TLC

Preparation of Tetrahydrofuranyl3,7,12-tris-(2-oxytetrahydrofuran)cholanoate (Cholic-THF)

To a 250-milliliter 3-necked round-bottomed flask, equipped with a50-milliliter pressure-equalizing addition funnel, nitrogen inlet,thermowell with digital temperature readout and a magnetic stirbar, wasadded 10.0 gram (0.0245 moles) of cholic acid, 2.46 gram (0.0098 moles)of pyridinium p-toluenesulfonate and 80 milliliter of anhydrous THF. Theaddition funnel was charged with 14.8 milliliter (0.196 moles) of2,3-dihydrofuran and 20 milliliter of anhydrous THF. The dihydrofuransolution was added over 45 minutes with no external cooling to thecholic acid suspension. A slight exotherm was observed. The resultingsuspension was stirred overnight at room temperature by which time ithad become a solution. The solution was diluted with 200 milliliter ofdiethylether and washed, in turn, with water, saturated sodiumbicarbonate solution, water and brine. The resulting organic layer wasstirred with anhydrous magnesium sulfate for 1 hour, filtered, andevaporated to a yellow oil. The oil was re-dissolved in 50 milliliter ofether and passed through a short column of sequential layers of silicagel, sodium carbonate, activated charcoal and Celite. The material waseluted with 300 milliliter of ether and the eluant evaporated on arotary evaporator to yield 14.9 grams of the title compound as a clearcolorless oil. TLC (75% ether/25% pentane) showed one spot (iodine) atR_(f) 0.65.

Preparation of 1,3-Adamantanediacetic Acid Substituted withα-angelicalactone

1,3-Adamantanediacetic acid (5.05 gram, 0.02 mole), α-angelicalactone(7.85 gram, 0.08 mole), and 10 milliliter anhydrous THF were placed in a100 milliliter round bottom flask equipped with a magnetic stirbar. Tothis mixture was added 100 milligram of p-toluenesulfonic acidmonohydrate and the mixture was heated to mild reflux under nitrogenwith stirring. After 17 hours, the solution was cooled to roomtemperature and quenched with 0.2 milliliter of concentrated ammoniumhydroxide. This solution was added dropwise into a mixture of 400milliliter of de-ionized water and 8 milliliter of concentrated ammoniumhydroxide solution. The precipitated material was re-dissolved in 50milliliter dichloromethane. This solution was washed with 50 millilitersaturated sodium bicarbonate solution followed by 50 milliliter ofsaturated sodium chloride solution and dried over anhydrous magnesiumsulfate for 30 minutes. The solvent was removed on a rotary evaporatorand the residue was dried under vacuum to give 3.50 grams of the titlecompound as a clear, colorless oil.

Control Positive Photoresist Formulation

A control positive CA photoresist was formulated containing 12% byweight of(3-(5-Bicyclo-[2,2,1]heptene-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanol)(NBHFA) homopolymer, 2% by weight Iodonium perfluorooctanesulfonate(1-PFOS) and 3% (MD-PFBUS) as the PAG, and 0.2% by weight tetrabutylammonium hydroxide (TBAH) in propylene glycol methyl ether acetate(PGMEA) solvent.

Experimental Positive Photoresist Formulation

An experimental positive CA photoresist was formulated containing 15% byweight of the DMA tetrahydrofuranyl3,7,12-tris-(2-oxytetrahydrofuran)cholanoate (preparation describedsupra), 12% by weight of(3-(5-Bicyclo-[2,2,1]heptene-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanol)(NBHFA) homopolymer, 2% by weight Iodonium perfluorooctanesulfonate(1-PFOS) and 3% (MD-PFBUS) as the PAG, and 0.2% by weight tetrabutylammonium hydroxide (TBAH) in propylene glycol methyl ether acetate(PGMEA) solvent.

Experimental Positive Photoresist Evaluation

A silicon substrate was coated with 3000 Å of the experimental positivephotoresist described supra. The coating was baked at between about 90°C.-110° C. for 1 minute to drive off the solvent. The coating was thenexposed at 193 nm (at doses ranging from about 15 mJ/cm² to about 100mJ/cm²) and post exposure baked at temperatures ranging from about 26°C. to about 90° C. for 1 minute. In all cases the photoresist coatingwas developed with 0.263 N tetramethyl ammonium hydroxide. Afterdevelopment, 130 nm line/130 nm space photoresist patterns showing sharpcontrast were obtained.

FIG. 2A is plot of photoresist thickness versus post exposure baketemperature for a control photoresist formulation. In FIG. 2A, thecontrol photoresist (NBHFA) described supra was coated on a substrateand baked after exposure at the temperatures indicated. Curve 200 givesthe photoresist thickness as a function of temperature beforedevelopment and curve 205 gives the photoresist thickness as a functionof temperature after development. Curve 205 is greater than zero becausethe style tool used to make the measurement could not register belowabout 100 Å. FIG. 2A shows that the exposed polymer of the controlphotoresist was soluble in aqueous developer over the entire postexposure bake temperature range.

FIG. 2B is plot of photoresist thickness versus post exposure baketemperature for an experimental photoresist formulation according to anembodiment of the present invention. In FIG. 2B, the experimentalphotoresist (NBHFA+Cholic-THF) described supra was coated on a substrateand baked after exposure at the temperatures indicated. Curve 210 givesthe photoresist thickness as a function of temperature beforedevelopment and curve 215 gives the photoresist thickness as a functionof temperature after development. Curve 215 is greater than zero becausethe Alpha Step tool used to make the measurement could not registerbelow about 100 Å. FIG. 2B indicates that the exposed polymer of theexperimental photoresist was prevented from dissolving (average thinningrate over the temperature range 70° C. to 144° C. was less than about0.6 Å/second) in aqueous developer by the added DMA until a temperatureof about 144° C., which is the thermal breakdown temperature of theprotecting groups of cholic-THF. The inhibition strength [dissolutionrate without DMA(DR_(o))/dissolution rate with DMA (DR_(A))] was 63,333.

FIG. 3 is plot of photoresist thickness versus actinic radiation dose asa function of post exposure bake temperature for an experimentalphotoresist formulation according to an embodiment of the presentinvention. The curves of FIG. 3 are also known as dose response curvesor contrast curves. In FIG. 3, a sample of the experimental photoresist(NBHFA+Chloic-THF) described supra, was coated on a silicon substrate,pre exposure baked at 90° C., exposed at 193 nm at the doses indicated,post exposure baked at 26° C. for curve 220, 50° C. for curve 225, 65°C. for curve 230 and 105° C. for curve 235 using a thermal gradientplate (TGP) and developed in 0.263 N tetramethyl ammonium hydroxide for60 seconds. The curves of FIG. 3 show that the photoresist compositionsusing DMAs of the embodiments of the present invention are relativelyhigh contrast photoresists and operate over a wide range of postexposure bake temperatures.

Thus, the embodiments of the present invention provide new photoresistcompositions having improved image resolution capability, improvedmethods of patterning substrates and improved DMA materials.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.Therefore it is intended that the following claims cover all suchmodifications and changes as fall within the true spirit and scope ofthe invention.

1. A dissolution modification agent represented by one of the followingstructures:

wherein each P¹, P², P³, P⁴, P⁵, P⁶, P⁷, P⁸, and P¹⁵ is independentlyselected from the group consisting of a structure V, a structure VI anda structure VII:

wherein each R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is independently selectedfrom the group consisting of a hydrogen atom, a hydrocarbyl group having4 to 12 carbon atoms, a substituted hydrocarbyl group having 4 to 12carbon atoms, a heterohydrocarbyl group having 4 to 12 carbon atoms, anda substituted heterohydrocarbyl group having 4 to 12 carbon atoms; andwherein any two R¹, R², R³ or any two R⁴, R⁵, R⁶ may be linked to form athree to eight-membered cyclic group.
 2. The dissolution modificationagent of claim 1, wherein said dissolution modification agent has theproperty of being insoluble in aqueous alkaline developer.
 3. Thedissolution modification agent of claim 1, wherein said dissolutionmodification agent has the property of being soluble in aqueous alkalinedeveloper after exposure to ultraviolet radiation.
 4. The dissolutionmodification agent of claim 1, wherein said dissolution modificationagent has the property of being soluble in aqueous alkaline developerafter exposure to ultraviolet radiation having a wavelength of about 250nm or less.
 5. The dissolution modification agent of claim 1, whereinsaid dissolution modification agent has the property of beinghydrophobic.
 6. The dissolution modification agent of claim 1, whereinsaid dissolution modification agent has the property of beinghydrophobic and becoming hydrophilic after heating to a temperatureabove 26° C. but no greater than about 100° C.
 7. The dissolutionmodification agent of claim 1, wherein said dissolution modificationagent is soluble in a solvent selected from the group consisting ofcyclohexanone, ethyl lactate, propylene glycol methyl ether acetate,gamma-butyrolactone and combinations thereof.
 8. The dissolutionmodification agent of claim 1, comprising: the structure (I).
 9. Thedissolution modification agent of claim 1, comprising: the structure(I); and wherein each P¹, P², P³ and P¹⁵ is structure (V).
 10. Thedissolution modification agent of claim 1, comprising: the structure(I); and wherein each P¹, P², P³ and P¹⁵ is structure (VI).
 11. Thedissolution modification agent of claim 1, comprising: the structure(I); and wherein each P¹, P², P³ and P¹⁵ is structure (VII).
 12. Thedissolution modification agent of claim 1, wherein: structure (I) is aglucoside; and wherein each P¹, P², P³ and P¹⁵ is a same ethoxyethylgroup.
 13. The dissolution modification agent of claim 1, wherein:structure (I) is a glucoside; and wherein each P¹, P², P³ and P¹⁵ is asame thetrahydrofuranyl group.
 14. The dissolution modification agent ofclaim 1, comprising: the structure (II).
 15. The dissolutionmodification agent of claim 1, comprising: the structure (II); andwherein each P⁵, P⁶, P⁷ and P⁸ is structure (V).
 16. The dissolutionmodification agent of claim 1, comprising: the structure (II); andwherein each P⁵, P⁶, P⁷ and P⁸ is structure (VI).
 17. The dissolutionmodification agent of claim 1, comprising: the structure (II); andwherein each P⁵, P⁶, P⁷ and P⁸ is structure (VII).
 18. The dissolutionmodification agent of claim 1, wherein: structure (II) is a citrate; andwherein each P¹, P², P³ and P¹⁵ is a same ethoxyethyl group.
 19. Thedissolution modification agent of claim 1, wherein: structure (II) is acitrate; and wherein each P¹, P², P³ and P¹⁵ is a samethetrahydrofuranyl group.
 20. The dissolution modification agent ofclaim 1, wherein: structure (I) is a glucoside; and wherein each P¹, P²,P³ and P¹⁵ is a same angelicalactone group.